Method of twisting expanded heat exchanger tubes



Feb. 13, 1968 T. F. PAULS 3,368,262

METHOD OF TWISTING EXPANDED HEAT EXCHANGER TUBES Filed June 2, 1965 v 4 Sheets-Sheet :3

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I IG-Q INVENTOR. THERON F PAL/LS ATTORNEY T. F. PAULS Feb. 13, 1968 METHOD OF TWISTING EXPANDED HEAT EXCHANGER TUBES 4 Sheets-Sheet 5 Filed June 2, 1965 INVENTOR. THE/PON F PAULS ATTORNEY Feb. 13, 1968 "r. F. PAULS 6 METHOD OF TWISTING EXPANDED HEAT EXCHANGER TUBES Filed June 2, 1965 4 s t s 4 9 INVENTOR.

THERON F PAULS ATTORNEY United States Patent Office 3,368,262 Patented Feb. 13, 1968 3,368,262 METHOD OF TWISTING EXPANDED HEAT EXCHANGER TUBES Theron F. Pauls, Godfrey, Ill., assignor to Olin Mathieson Chemical Corporation, a corporation of Virginia Continuation-impart of application Ser. No. 287,240, June 12, 1963. This application June 2, 1965, Ser. No. 460,705

3 Claims. (Cl. 29-157.3)

This application is a continuation-in-part of my copending application Ser. No. 287,240, filed June 12, 1963, now U. S. Patent No. 3,273,227.

This invention relates generally to the fabrication of heat exchange devices and more particularly to the fabrication of single piece sheet metal heat exchange structures having multiple parallel tubes.

A commonly used and eflicient type of heat exchange unit for evaporators, air conditioning, condensers, internal combustion engine cooling radiators, and the like is formed from a plurality of superimposed sheets of metal having internally disposed between the sheets a number of conduits generally in a parallel spaced arrangement extending from a first or intake header to a second or outlet header. One or more of such units may be employed; the conduits or tubes serve to carry a heat exchange medium such as Water or other coolant in conductive relationship with another medium such as air or other gas passing between the tubes. This type of construction is typical of automobile radiators where, for example, the heated water issues from the cooling block of the engine with the aid of a pump, first enters one of the two headers, and then passes through a great number of thin-walled, relatively flat, closely spaced tubes between which cooling air is blown and which extend usually vertically from one to the other of the headers. Condensers are also frequently of this same type of construction.

According to one known method of manufacture as illustrated in US. Patent 2,690,002, this type of heat exchange unit may be readily manufactured to provide a great multiplicity of tubes in a sheet of metal. This method involves the application of a suitable predetermined pattern of weld-inhibiting material between component sheets, pressure welding all adjoining areas except those separated by the weld-inhibiting material, thereby forming a unified composite panel, and inflating along the unwelded areas to erect the tubes integral with the resultant tubed panel. Full advantage heretofore has not been taken of this method inasmuch as the tubes formed are of rather flat or oval shape with the major dimensions lying within or parallel to the panel in which the tubes are formed. In many applications it is desirable that the tubes extend not only longitudinally but also extend perpendicularly out of the panel to a considerable extent so as to place a greater number of the tubes in spaced parallel relationship rather than a lesser number in the same plane. This design adapts the units to fabrication as single pieces of large size, a lesser number of which may then be put together for installations where the external mediumpasses through perforations in the panel transversely to it rather than passing parallel to the panel along its surfaces.

In accordance with the concepts of this invention, a sheet metal panel is formed according to the procedure of the above-mentioned US. Patent 2,690,002, to form the desired tubular passageway system in its embryonic form. This panel is then slit along a plurality of parallel spaced apart lines extending between two oppositely disposed headers to define the interconnecting tubes. The tube portions lying between adjacent slits are then bent or twisted out of the normal plane of the panel in a novel manner so as to dispose the tube portions in substantially perpendicular relationship to the plane of the panel.

The rotation of these tube portions is most expeditiously done by inserting into each of the headers a combshaped element having teeth which extend into the interior of each of the tubes, and then rotating the tubes from the outside the desired amount. As will become evident, this method achieves the desired positioning of the tubes as well as overcoming various objections to other available methods of rotating the tubes.

In order to improve the heat transfer characteristics of the device, secondary heat dissipating fin material may be inserted between the parallel opposing surfaces or rolls of adjacent tubes and secured in place as by brazing or soldering. This construction, while extremely simple to fabricate and assemble, presents a practical and highly efiicient heat exchanger adapted to provide a maximum amount of external heat exchange medium flow between the tubes with a minimum amount of turbulence or im pediment thereto.

Having thus generally described the invention it becomes a principal object thereof to provide a method of producing an efficient heat exchange device adapted for transfer of heat between an internal and external heat exchange medium.

Another object of the present invention is to provide a method of producing a heat exchange device having a plurality of parallel heat transfer tubes interconnected between a pair of headers for maximum flow of an internal heat transfer medium.

Still another object of the present invention is to provide a method of producing a heat transfer device having a plurality of heat transfer tubes interconnected between a pair of headers, the tubes being elongate in cross-section with the cross-sectional major dimension of the tube being disposed at substantially right angles to the normal plane of the panel from which the device is fabricated.

Still another object of the present invention is to provide a method of producing a heat exchange device having a plurality of heat transfer tubes interconnected between a pair of oppositely disposed headers which are bent or twisted out of the normal plane of the panel from which the device is fabricated so as to provide slots or apertures through which an external heat transfer medium may flow unimpeded over the external surfaces of th heat transfer tubes.

It is still a further object of the present invention to provide a method of producing a heat exchange device having a plurality of heat transfer tubes interconnected between a pair of headers and having the major crosssectional dimension disposed at substantially right angles to the normal plane of the panel from which the device is fabricated to provide elongate apertures in which secondary heat dissipating fin stock material is inserted in heat transfer relationship with the outer walls of the tubes to achieve maximum efficiency of heat exchange between the internal and external heat transfer mediums.

Still another object of the present invention is to provide a method of producing a device of the above character in a minimum number of steps of simplified nature.

Further objects and advantages of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings, in which:

FIGURE 1 is a plan view of one embodiment of the completed heat exchange device of this invention;

FIGURE 2 is a composite plan view illustrating a num ber of steps involved in the fabrication of the device of FIGURE '1;

FIGURE 3 is a sectional view taken on line 3e-3 of FIGURE 2;

FIGURE 4 is a view similar to FIGURE 3 illustrating the device in an intermediate stage of fabrication;

FIGURE 5 is a fragmentary view similar to FIGURE 4, but on an enlarged scale, illustrating a further stage in the fabrication of the device;

FIGURE 6 is a fragmentary sectional view on an enlarged scale taken on line 6-6 of FIGURE 1;

FIGURE 7 is a fragmentary sectional view on an enlarged scale taken on line 7-7 of FIGURE 1;

FIGURE 8 is a partial plan view of the panel of FIG- URE 2 after inflation of the tubes; and

FIGURE 9 is a partial plan view of the panel of FIG- URE 8 illustrating the tubes in their position after rotation thereof.

Referring now to the drawings and particularly to FIGURE 1, there is seen an illustrative embodiment of this invention which is a heat exchange device generally indicated by the reference numeral 10. The initial stage of fabrication of this device is substantially as set forth in great detail in the above-mentioned U.S. Patent 2,690,002, and is generally illustrated, in conjunction with other steps in the formation of the heat exchange device 10, in FIGURES 2, 3 and 4.

Referring now to FIGURE 2, it will be seen that the heat exchange device 10 is initially formed from a plurality of superimposed fiat metal sheets 12 and 14. Sheet 12 has applied thereto a pattern of weld-preventing material 16 which is a foreshortened version of the desired pattern of tubular passageways in the finished article. This pattern consists of a pair of parallel bands 18 and 20 which are spaced apart adjacent a pair of opposite edges of the stack of sheets formed by the individual sheets 12 and 14. Interconnecting the two bands 18 and 20 are a plurality of bands 22 of weld-preventing material which cover the extent of sheet 12 intermediate bands 18 and 20 except for elongated parallel islands 24 which are free of weld-preventing material, and which also extend between the aforementioned bands 18 and 20. It will become apparent that the bands 18 and 20 of weld-preventing material correspond to the headers in the finished article and that the bands 22 correspond to the plurality of interconnecting tubes. In order to provide ingress and egress apertures for a heat transfer medium, the bands 18 and 20 may be extended to an edge of sheet 12 as indicated at 26. It will also be seen that a marginal portion of sheet 12 along opposite sides transverse to the aforementioned opposite sides has been left free of weldpreventing material 16 forming a peripheral marginal area 28 with the exception of the two strips 26 extending to one of the transverse edges for the ultimate provision of openings adapted for connection to an external source of heat transfer medium.

The stack of component sheets 12 and 14 with weldpreventing material 16 sandwiched therebetween is then temporarily secured together as by clamps, spot welding or the like to prevent relative movement between the sheets 12 and 14. The assembly thus formed is then heated to a required temperature and fed through a pair of pres sure rolls which exert sufiicient pressure on the stack to firmly weld the sheets 12 and 14 together into a single integrated sheet in the areas not coated with the weldpreventing material 16. Simultaneously with the bonding operation the sheets 12 and 14 undergo a substantial reduction in thickness as well as an elongation in the direction of rolling whereby the foreshortened pattern of Weld-preventing material is stretched to a length corresponding to the desired pattern of tubular passageways in the finished article. FIGURE 4 illustrates in cross section the unified sheet 30 with the unwelded portions 32 at this stage of the fabrication.

Referring again to FIGURE 2, it will be seen that a plurality of slits 34 are formed in the islands 24 free of weld-preventing material, the slits extending almost the vided in the transverse marginal area free of weld-preventing material for a purpose hereinafter to become apparent. The slits 34 and 36 may be formed during any desirable stage of the fabrication process, either in the individual sheets 12 and 14, or after the sandwich of sheets 12 and 14 and weld-prevening material 16 has been formed and temporarily secured together or still alternatively after the aforementioned hot rolling step. Preferably the last mentioned alternative would be selected so as to eliminate both the problem of proper alignment of individual sheets 12 and 14 with slits already formed therein, and the problem of rewelding of adjacent slit edges during the hot rolling step if no weld-preventing material is inserted between these edges. However, it is apparent that the article is readily adaptable to any of a number of arrangements of the aforementioned steps to achieve the heat exchange device in its embryonic form as illustrated in cross-section in FIGURE 4.

Subsequent to the pressure welding stage in the fabrication process, the unwelded areas 26 which extend to the transverse edge of the unified sheet 30 are mechanically pried open and a suitable nozzle is inserted therein and connected to an external source of pressure fluid. The pressure fluid is pumped into the unwelded portions defined by the weld-preventing material 16 to expand the sheets 12 and 14 over these portions and thereby create the desired system of internal fluid passageways. The expansion may be carried out either without external restraint thereby resulting in passageway walls having a substantially rounded configuration, or preferably the expansion may be carried out with the composite sheet 30 inserted between suitable dies or platens, either flat or shaped, so as to limit the extent to which the passageway walls can expand outwardly, thus creating .a tubular passageway of generally rectangular configuration in crosssection as seen in FIGURE 5. The heat exchange device now consists essentially of the flat unified sheet 30 with an expanded pattern of tubular passageways corresponding to the original pattern of weld-preventing material 16, with the bands 18 and 20 forming the headers 40 and 42.

Referring again to FIGURE 1, the heat exchange device 10 comprises the integrated sheet 30 of generally rectangular configuration, having the parallel spaced-apart internally disposed headers 40 and 42 and the elongate tubular passageways 38. The headers 40 and 42 terminate adjacent an edge of sheet 30 in inlet and outlet openings 44 and 46 respectively to which conduits 48 and 50 respectively are connected for communication of the heat exchange device with a source of internal heat transfer medium.

It will be seen from FIGURE 1 and in greater detail in FIGURE 6 that the tubular passageways 38 have been twisted out of the normal plane of sheet 30 so as to dis pose the major cross-sectional dimension of tubes 38 at approximately right angles to the normal plane of sheet 30. The disposition of tubes 38 is of an extent covering substantially all of the length of the slits 34 previously formed in the unified sheet 30, and is accomplished by a unique method to be described shortly. Thus, in the finished product, the individual tubes 38 are disposed with opposed parallel outer wall surfaces 52 in spaced apart relationship, providing relatively wide and elongate slots or apertures 54 through which an external heat transfer medium can flow substantially unimpeded. Communication between the headers 40 and 42 and interconnecting tubes 38 is maintained through the interior of the tubes 38 which traverses the transition portions 56 of tubes 38 which lie between the point of connection between the headers 40 and 42 and the remainder of the tubes 38 which are disposed in the aforementioned perpendicular relationship. Of course, it is desirable to maintain these transition portions 56 as short as possible within the limits of the bending characteristic of the metal in order to provide the maximum length of apertures 54 for unimpeded flow of air and, as will be seen in more detail hereinbelow,

to provide the maximum amount of space for secondary heat dissipating fins.

When the tubular passageways have been completed and the interconnecting tubes 38 bent to the desired relationship secondary heat dissipating fins 58 formed of closely corrugated or pleated fin stock may be inserted and positioned within the elongate spaces or apertures between the opposing faces 52 and tubes 38, and suitably secured therein by conventional means, such as solder, brazing and the like interposed between the panel and the fin stock. It will be noted from FIGURE 6 that when the tubes 38 are bent, the welded portions of sheets 12 and 14 formerly defined by the islands 24 free of weld-preventing material now constitute oppositely directed flanges 60, thereby leaving the opposing faces 52 of tubes 38 smooth and free of any projecting obstructions. Consequently, it is a relatively simple matter to slip the strips of fin stock 58 into place between adjacent tubes for subsequent unification therewith as explained above. In addition the flanges 60 add structural rigidity to the device and also reinforce the leading edge of the tubes for minimizing damage thereto due to stones or other foreign objects which can strike the frontal area of an automotive radiator. Also the flanges constitute additional heat transfer stock.

In order to secure the outermost rows of fin stock 62 and 64 in place, outer' retaining strips 66 and 68 are formed by providing the two outermost slits 36 (FIG- URE 1) beyond the pattern of weld-preventing material 16. Thus, during the hot rolling process a strip of sheets 12 and 14 is bonded together between the outermost slits 36 and adjacent slits 34 which, when twisted in the same manner as tubes 38, form the outer retaining strips 66 and 68 respectively.

Considering now the precise method by which the previously inflated tubes may be rotated, reference is had to FIGURES 8 and 9 of the drawings. As has been noted hereinbefore, the tubes 38 will have been inflated and the slitting operation performed to yield the slits 34 and 36, as is shown in FIGURE 8. A comb-shaped element may then be inserted into each of the headers 40 and 42 for a purpose to become evident shortly. As can be seen in FIGURE 8 of the drawings, the comb-shaped element 70 consists of a straight shank portion 71 equal in length to the length of the header portions 40 and 42, and an extension of such shank portion projecting from the headers, as at 72. Mounted upon the shank portion 71 are a plurality of projecting teeth 73, each of a length slightly less than the width of the header 40 or 42. An element 70 may be inserted laterally into the header from the open end thereof, as shown in FIGURE 8 with respect to header 40. The element 70 may then be moved laterally such that the projecting teeth 73 are moved into the interior of the tubes 38, as shown in FIGURE 8 with respect to header 42.

Following rotation of the tubes into the position shown for example in FIGURE 9, the comb element 70 may be moved from the position with its teeth within the tubes as shown in the lower portion of FIGURE 8 back into the header portion, for example as shown in the upper portion of FIG-URE 8, and then removed by sliding same out of the header through the open end thereof.

The primary advantage of the above-described method is that the presence of the teeth 73 within the interior of the tubes 38 assures that the transitional areas of the tubes 38 near the headers 40 and 42 remain open during the subsequent rotation of the tubes. The rotation of the tubes may be done in any suitable manner, as by grasping them with a suitable tool from the outside and rotating them the desired amount. It will be evident that upon rotation of the tubes 38 and retaining strips 66 and 68, allowed for by the presence of slits 34 and 36, the greatest amount of twisting or bending would occur in the transitional area near the headers 40 and 42. Were it not for the presence of teeth 73 the tubes 38 in such areas would become greatly deformed, and perhaps even closed, and would thus require reopening after rotation.

It will be evident that the comb element employed in this-invention may take a variety of forms, and that the one shown is merely exemplary. For example, the one illustrated includes teeth 73 having a width substantially equal to the width of tubes 38. Accordingly, the teeth 73 within the transitional portion of tubes 38 would rotate in response to the rotation of the tubes 38. Thus, the composition of the teeth 73 must necessarily be of a material capable of such rotation; any desirable flexible and resilient material which would still resist the closing of the tubes in the transitional area may be employed. If so desired, the width of the teeth 73 may be substantially decreased and thus each may consist for example of a small, round, pin-shaped element projecting into each of the tubes 38. In such a modification, the material of the teeth may be rigid and serve merely to assure an opening through the transitional portion of the tubes 38 as the tubes are rotated about the pins.

As illustrated in the drawings, the various teeth are inserted into the tubes 38 simultaneously. However, it is also possible to provide the comb element with means for sequentially inserting the teeth individually and similarly retracting them after the rotation operation is performed.

It should be noted that with any of the above embodiments and alternate methods of fabrication, as much cooling capacity as required may be achieved by arrang ing the heat exchange units in multiples with the headers of the several units being connected in parallel.

It will be apparent from the foregoing description and accompanying drawings that there has been provided a method for producing a heat exchanger which is believed to provide a solution to the foregoing problems and achieve the aforementioned objects. It is to be understood that the invention is not limited to the illustrations described and shown herein which are deemed to be merely illustrative of the best modes of carrying out the invention, and which are susceptible of modification of form, size, arrangement of parts, and detail of operation, but rather is intended to encompass all such modifications as are within the spirit and scope of the invention as set forth in the appended claims.

What I claim and desire to secure by Letters Patent is:

1. A method for producing a heat exchange device from a composite sheet formed of two superposed planar sheets having a pattern of weld-inhibiting material interposed between said sheets, said pattern including a pair of parallel spaced-apart bands located adjacent opposite edges of said composite sheet and extending to a transverse edge of said sheet and a plurality of closely spacedapart bands lying parallel to said transverse edge and joined at opposite ends with said pair of bands, said pair of bands and plurality of bands thereby defining islands free of said weld-inhibiting material, said method comprising the steps of (A) slitting said composite sheet in said weld-inhibiting material free islands over a major portion of the length thereof to provide a plurality of individual strips of said composite sheet,

(B) forming a system of hollow tubes in said composite sheet corresponding to said pattern of weldinhibiting material by applying thereto a fluid under pressure to expand the areas of said composite sheet covered with said weld-inhibiting material,

(C) inserting into the ends of the tubes corresponding to the plurality of bands a plurality of members having an exterior configuration substantially matching the interior configuration of said tubes, and

(D) rotating said hollow tubes from the exterior there of to dispose said tubes in a plane substantially perpendicular to the plane of said composite sheet.

2. A method of producing a heat exchange device from a composite sheet formed of two superposed planar sheets having a pattern of weld-inhibiting material interposed between said sheets, said pattern including a pair of first bands in parallel spaced-apart relationship located adjacent opposite edges. of said composite sheet and extending to a transverse edge of said sheet, and a plurality of second bands in closely spaced-apart relationship lying parallel to said transverse edge and joined at opposite ends with said first bands, said first bands and second bands thereby defining islands free of said weld-inhibiting material, said method comprising the steps of (A) slitting said composite sheet in said weld-inhibiting material free islands over a major portion of the length thereof to provide a plurality of individual strips of said composite sheet,

(B) forming a system of hollow tubes in said composite sheet corresponding to said pattern of weldinhibiting material by applying thereto a fluid under pressure to expand the areas of said composite sheet covered with said weld-preventing material, said system of hollow tubes comprising (1) a pair of first tubes corresponding to said pair of first bands, and

(2) a plurality of second tubes corresponding to said plurality of seconds bands,

(C) inserting into each of said first tubes a combshaped member having teeth thereon in alignment with each of said second tubes,

(D) moving said comb-shaped element within said first tubes to bring the teeth into the interior portion of each of said second tubes,

(E) rotating each of said second tubes from the exterior thereof to displace the elongate portion of said second tubes out of the normal plane of said composite sheet, thereby forming elongate apertures between adjacent confronting surfaces of said second tubes, and

(F) removing the comb-shaped element from said first tubes.

3. A method as set forth in claim 2 further including the steps of inserting secondary heat exchange fin stock into said apertures between said confronting surfaces and securing said fin stock to said surfaces.

References Cited UNITED STATES PATENTS 2,856,164 10/1958 Adams 29157.3 2,957,679 10/1960 Campbell 29157.3

FOREIGN PATENTS 1,238,450 7/1960 France.

JOHN F. CAMPBELL, Primary Examiner.

P. M. COHEN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,368,262 February 13, 1968 Theron F. Pauls It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 75, after "almost the" insert full length of these islands. An additional slit 36 is procolumn 4, line 6, for "weld prevening" read H weld-preventing Signed and sealed this 15th day of April 1969.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

1. A METHOD FOR PRODUCING A HEAT EXCHANGE DEVICE FROM A COMPOSITE SHEET FORMED OF TWO SUPERPOSED PLANAR SHEETS HAVING A PATTERN OF WELD-INHIBITING MATERIAL INTERPOSED BETWEEN SAID SHEETS, SAID PATTERN INCLUDING A PAIR OF PARALLEL SPACED-APART BANDS LOCATED ADJACENT OPPOSITE EDGES OF SAID COMPOSITE SHEET AND EXTENDING TO A TRANSVERSE EDGE OF SAID SHEET AND A PLURALITY OF CLOSELY SPACEDAPART BANDS LYING PARALLEL TO SAID TRANSVERSE EDGE AND JOINED AT OPPOSITE ENDS WITH SAID PAIR OF BANDS, SAID PAIR OF BANDS AND PLURALITY OF BANDS THEREBY DEFINING ISLANDS FREE OF SAID WELD-INHIBITING MATERIAL, SAID METHOD COMPRISING THE STEPS OF (A) SLITTING SAID COMPOSITE SHEET IN SAID WELD-INHIBITING MATERIAL FREE ISLANDS OVER A MAJOR PORTION OF THE LENGTH THEREOF TO PROVIDE A PLURALITY OF INDIVIDUAL STRIPS OF SAID COMPOSITE SHEET, (B) FORMING A SYSTEM OF HOLLOW TUBES IN SAID COMPOSITE SHEET CORRESPONDING TO SAID PATTERN OF WELDINHIBITING MATERIAL BY APPLYING THERETO A FLUID UNDER PRESSUE TO EXPAND THE AREAS OF SAID COMPOSITE SHEET COVERED WITH SAID WELD-INHIBITING MATERIAL, (C) INSERTING INTO THE ENDS OF THE TUBES CORRESPONDING TO THE PLURALITY OF BANDS A PLURALITY OF MEMBERS HAVING AN EXTERIOR CONFIGURATION SUBSTANTIALLY MATCHING THE INTERIOR CONFIGURATION OF SAID TUBES, AND (D) ROTATING SAID HOLLOW TUBES FROM THE EXTERIOR THEREOF TO DISPOSE SAID TUBES IN A PLANE SUBSTANTIALLY PERPENDICULAR TO THE PLANE OF SAID COMPOSITE SHEET. 